Separate branches of the uvr gene-dependent excision repair process in ultraviolet-irradiated Escherichia coli K-12 cells: their dependence upon growth medium and the polA, recA, recB, and exrA genes
The extent of repair of single-strand breaks (incision breaks) induced in the deoxyribonucleic acid (DNA) of Escherichia coli K-12 cells by the uvr gene- dependent excision repair process after ultraviolet (uv) radiation was determined in the wild-type, polA1, recA56, recB21, and exrA strains. The wild-type strain repaired all incision breaks after incident doses of uv radiation (254 nm) of ~60 J m/sup -2/ or less when incubated in growth medium, or ~15 J m/sup -2/ or less when incubated in buffer. The polA1 strain repaired the incision breaks completely after incident doses of ~12 J m/sup -2/ or less when incubated in growth medium, or after ~4 J m/sup -2/ when incubated in buffer. The recA13, recB21, and exrA strains showed essentially complete repair after incident doses of 10 to 15 J m/sup -2/ whether the cells were incubated in buffer or growth medium. These results suggest that the uvr genedependent excision repair process may be divided into two branches, one which is dependent on the presence of growth medium and also the rec/sup +/ exr/sup +/ genotype, and a second which can occur in buffer (growth medium-lndependent) and is largely dependent on DNA polymerase I. The presence of chloramphenicol in the growth medium resulted in an inhibition of the growth medium-dependent repair occurring in wlld-type and polA1 cells and had little or no effect on the extent of repair observed in recA56, recB21, or exrA cells. The similarities between the growth medium-dependent and - independent branches of excision repair and two known processes for the repair of x-ray-induced singlestrand breaks are discussed. (auth)
- Research Organization:
- Stanford Univ. School of Medicine, CA
- NSA Number:
- NSA-29-018582
- OSTI ID:
- 4345382
- Journal Information:
- J. Bacteriol., v. 117, no. 2, pp. 717-725, Journal Name: J. Bacteriol., v. 117, no. 2, pp. 717-725; ISSN JOBAA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
*ESCHERICHIA COLI-- BIOLOGICAL RADIATION EFFECTS
*STRAND BREAKS-- RADIOINDUCTION
BIOLOGICAL EFFECTS
BUFFERS
CHLORAMPHENICOL
CULTURE MEDIA
GENES
GENOTYPE
N48310* --Life Sciences--Radiation Effects on Microorganisms- -Basic Studies
PHOTON BEAMS
ULTRAVIOLET RADIATION
X RADIATION RADIOINDUCTION